1. Field of Invention
This present invention generally relates to cerebrospinal fluid (CSF) shunts and, more particular, to a device and method for testing for the presence, absence and/or rate of flow in the shunt tubing implanted under the skin.
2. Description of Related Art
Approximately 69,000 people are diagnosed with hydrocephalus each year in the United States [1]. There are approximately 300,000 shunted hydrocephalus patients in the US [3][4].
The one-year shunt failure rate of shunts is approximately 40% [15, 16], and the mean period to failure is typically only 5-10 years [17]. Obstruction of the ventricular catheter is overwhelmingly the greatest cause [4, 15, 18-20]. Since catheter replacement requires surgery, a need for shunt revision must be reasonably established. Hydrocephalus is a condition of CSF dysregulation, resulting in accumulation of fluid in the brain ventricles. It can lead to neurodegeneration and death if untreated. It is most commonly treated by diverting CSF to the peritoneal cavity by means of a permanent prosthetic shunt.
The usual clinical manifestations of shunt failure (headaches, vomiting) are non-specific, making shunt obstruction difficult to differentiate from less serious illnesses, particularly in pediatric patients in whom three false alarms are seen for every true malfunction [4]. Physical examination, including pumping of the shunt reservoir, is unreliable [21]. CT (computed tomography) remains the gold standard [4, 9], however advanced imaging techniques produce static results, are expensive and cannot be used to investigate every headache, and result in repeated radiological exposures of patients (often children). Current dynamic measures of shunt flow generate only bivariate analyses of “flow” or “no flow” (FIG. 7). New technologies under development are complex (ultrasound tracking of bubbles), lacking in precision (FLIR) or require implantation (implanted thermal flow technologies) and have not reached the clinic.
Thus, there remains a need for a device capable of determining absolute CSF flow rate which has two clinically important applications that are not possible with imaging or bivariate flow measures: (1) prediction of impending catastrophic shunt failure, i.e., monitoring shunt flow in routine examinations enables early recognition of a diminishing flow rate trend in a failing shunt and pre-emption of catastrophic failure; and (2) monitoring and adjusting shunt valve settings to accommodate individual needs for CSF drainage. The degree of impairment in draining CSF varies from hydrocephalic patient to patient. Adjustable shunt valves avoid under drainage and over drainage by the shunt. While the settings for these valves in each patient must currently be determined empirically over a number of weeks, the invention of the present application provides guidance to neurosurgeons and quicker stabilization of CSF homeostasis. In addition to these clinical applications, the shunt flow detection device developed here provides an important research tool for CSF flow behavior in hydrocephalus patients.
All references cited herein are incorporated herein by reference in their entireties.